Corresponding shafts and bearings are found in many different forms, especially in transmissions, but also in simple motor drives and generators.
What is often important for operating a machine is the particular torque which is transmitted at the moment by a drive shaft. This is expedient, for example, in order to control output, to limit mechanical loads, to minimize wear and to reduce risks of damage.
Torsion sensors are already known for this purpose from the prior art and are based on various technologies.
DE 69834528 P2 discloses a magnetostrictive torque sensor, in which a magnetostrictive ring consisting particularly of a composite material based on rare-earth, iron or similar alloys is attached onto or inserted into a shaft. In the torque-free state, an azimuthally revolving magnetic field prevails within the ring and is disrupted by torque being introduced, thus giving rise to a resulting axial magnetic field as an indicator of the torque.
DE 102005006769 A1 shows, in general, as a reversal of magnetostriction, the Villary effect, as it is known, by means of which deformation, for example torsion of a shaft, gives rise to a magnetic action of the shaft. Materials exhibiting a Villary effect which are mentioned are iron, copper, nickel or alloys of these metals.
DE 102205010338 A1 discloses a force sensor arrangement, with magnetostrictive resistance sensors, an inhomogeneous layer sequence of magnetic layers being provided, on which a magnetostrictive action is exerted. An electrical resistance is subsequently measured in the overall arrangement as a measure of deformation.
Japanese patent abstract no.: 2001033322 A discloses a rolling bearing, on the inner ring of which magnetostrictive elements are arranged, magnetic sensors being provided on the inside of the outer ring of the bearing. The torque acts on the elements in the bearing inner ring and is thus intended to cause a change in the magnetic conditions.
EP 1046893 B1 basically discloses the use of the magnetostrictive effect for torque measurement and the fastening of a magnetostrictive ring element on a shaft for transmitting the torque and for utilizing the effect. However, this does not describe any structure directly related to the set-up of a rolling bearing into which a torque sensor is integrated. For measuring the magnetic field, a special sensor is described by means of which a saturation magnetization of a probe is measured with high frequency in various magnetization directions, with the result that the magnetic field, as a result of the magnetostrictive element, can be measured exactly.
Against this background, the set object of the present invention is, for a shaft arrangement with a rotatable shaft which is mounted in a rolling bearing with rolling bodies and with an outer ring, to carry out torsion measurement in as space-saving a way as possible and especially simply in structural terms.